Thermopile sensors produce a voltage that is proportional to the power of the incident infrared (IR) radiation. Because all objects emit IR radiation, a thermopile can be used to measure the temperature of an object without directly contacting the surface of the object. FIG. 1 depicts an example of an individually packaged thermopile sensor 10 that includes a sensor element 12, a package 14, and connections leads 16.
The IR radiation that is detected by a particular thermopile sensor is a function of the view angle, φ, of the thermopile sensor. FIG. 2A depicts a side view of a thermopile sensor 10 and its view angle relative to an object 20 of interest. For purposes of this description, the view angle and the distance, d, between the thermopile sensor and the object define the field of view 22 of the thermopile sensor relative to the object. FIG. 2B depicts a front view of the field of view from FIG. 2A relative to the object.
While thermopile sensors work well to detect the temperature of an object, their ability to provide temperature information is limited to the field of view of the particular device.